Patients that require critical care in a hospital or other medical facility are often in a bed surrounded by various electronic monitoring and lifesupporting devices used to monitor their progress and assist their recovery. These devices may include such equipment as ventilators, intra-venous (I.V.) pumps, and cardiac monitors, among various other devices, and may sometimes include a computer terminal and automated nurse information system to readily supply information about the patient to the medical staff. All of these devices must be supplied with electrical power by some means.
Normally, each critical care device has a power cord which is plugged into a wall or floor outlet in close proximity to the hospital bed containing the patient. Oftentimes, when the head of the hospital bed abuts against a wall, the medical devices must be placed at the foot of the bed to leave room on the bed sides, referred to as point-of-care zones, for medical personnel to attend to the patient. In such a scenario, the power cords that extend between the wall and each necessary device at the foot of the bed collectively clutter the floor area in the point-of-care zones. These cords possibly can become tangled around the bed or cause an impediment to medical personnel working in the point-of-care zones.
Additionally, in a critical care situation, it is often necessary for the patient to be moved quickly into another room within the medical facility to gain access to necessary life-sustaining or monitoring equipment which is either too cumbersome to be mobile or is too expensive for the hospital to have a unit for each critical care patient. When such a situation arises, the medical personnel must usually unplug all of the support devices, gather all the associated power cords together, arrange the cords into a manageable movable group, and move the patient and the devices to a different area where the devices all must again be plugged into a wall or floor power source. This slows down the patients' movement and increases the manual workload for hospital personnel who should be focusing upon the patient. Additionally, a large number of people are necessary to move a patient requiring many monitoring devices because the monitoring or other life-supporting devices are usually powered by a wall or floor power source and are normally moved independent of the bed and patient.
Other problems arise when the patient is moved to a room where the number of wall or floor outlets within the vicinity of the bed is not sufficient to support the number of life-support devices which the patient needs. In such a situation it becomes necessary to use an extension cord to reach an outlet located outside the vicinity of the bed. This, in turn, further increases the cord clutter around the bed and the possibility of unplugging a power cord.
Many critical care beds are electrically motorized so that the patient or medical attendant may adjust the position of the bed by a remote switch or control. The beds are powered by a cord which runs from a wall or floor outlet to the bed. Since the beds are receiving power for the motorized position control units, one proposed solution to the problem of too few electrical outlets around a bed for the necessary devices and the problem of power cord clutter is to have several electrical outlets located somewhere on the hospital bed frame which are powered by the A.C. power running to the bed for the position control unit. Power outlets located at the foot of the bed frame would reduce the number of cords that clutter the point-of-care zones around the bed. Unfortunately, using the bed essentially as an extension cord increases the risk of shock to the patient due to the increased amount of load current that is being drawn through the bed circuitry to power the support devices. Ironically, this increased shock hazard is the result of a protective wiring scheme used on many hospital bed frames to reduce the risk of electrical shock to a patient from the bed control circuitry.
Normally, to protect patients from receiving an electrical shock when they come into contact with a motorized hospital bed, the frame of the bed is connected to earth ground at the wall or floor power source. Grounding the frame reduces the possibility of a dangerous electrical potential developing on the frame and, consequently, reduces the risk of shock to the patient because the earth ground will draw off any excess charge from the frame. However, in the three-wire configuration utilized in the electrical systems of most commercial buildings, including hospitals, the earth ground wire is normally connected to a neutral wire somewhere in the system, while a hot or "live" wire supplies power at the outlet. The hot, neutral and ground wires run essentially adjacent and parallel along their lengths throughout the building, and therefore, the three conductors are insulated from each other by a plastic or rubberized coatings to prevent shorting between the conductors. However, due to the imperfect insulation qualities of the coatings, and the imperfect isolation of charge in the medical devices that are drawing current from the wires, a certain amount of undesirable leakage current develops on the neutral wire as it is conducting electricity. That is, current leaks through the insulation onto the neutral wire from the hot wire and through the electrical components and circuitry of the bed and medical devices on the neutral wire. Since the earth ground wire is electrically connected to the neutral wire, the earth ground wire also carries this leakage current. As a result, the hospital bed frame develops a leakage current thereon because it is grounded to the power supply ground or building earth ground, and this current presents a risk of shock to a patient in the bed.
Usually, in a motorized hospital bed, the only leakage current that is of any magnitude is associated with the bed position controls and motors. This current is kept to a minimum by appropriate circuitry design. However, connecting of other medical devices to the bed frame to draw power through the bed power supply increases the leakage current on the bed frame to an unsafe level because these external devices are not optimally designed to prevent leakage current. It only takes a very low current flow, essentially a current in the milliampere range, to disrupt the normal beating of the human heart. While the possibility of shock is undesirable with any patient, the situation becomes especially acute with critical care patients with heart conditions. Additionally, the more critical patients require a large number of monitors and life-sustaining devices, and each additional electronic support device which is supplied with power through the bed power supply increases the leakage current and increases the risk of shock to the patient. Underwriters Laboratories medical specifications require that the leakage current on a hospital bed frame be below 100 microamperes for motorized critical care beds. However, while the leakage current associated with the bed position controller may be contained below this range by the bed designers, this low current may not be achievable with currently available beds when additional monitoring and support devices are powered from the bed power supply because the manufacturers of the external medical devices are not necessarily concerned with leakage current.
Therefore, there has always been a tradeoff between eliminating the clutter of power cords and electrical connection equipment around the bed and reducing the likelihood of electrical shock to the patient. As may be appreciated, the health of the patient is paramount, and therefore, tidiness and efficiency around the bed may have been sacrificed in order to achieve a lower amount of leakage current in the bed frame.
Furthermore, approximately 70% of all the life-support and monitoring equipment used by the patient while the bed is stationary, must have power when the patient and hospital bed are in transit between rooms. In the past, each device has been powered apart from the bed and has had to have an internal power supply for when the cord is unplugged from the wall. The internal supplies increase the weight and cost of the device and are subject to expiring at different times. It is thus desirable to supply all of the external medical devices with power when the main bed power cord has been removed from the wall or floor outlet and the patient and bed are moving between rooms.
Consequently, it is an objective of the present invention to electrically power various life-support and monitoring devices directly from the hospital bed frame to reduce the necessary power cords and electrical connections at a wall or floor source.
It is further an objective of the present invention to provide outlets on the bed frame which supply both A.C. and D.C. power for the various external monitoring and support devices that are normally located around a critical care hospital bed.
It is still further an objective of this invention to reduce the power cord clutter around the hospital bed in the "point-of-care" zones where the medical personnel must move to attend to the patient.
It is yet another objective of the present invention to provide an uninterrupted power supply to external medical devices while the bed is in transit and the main bed power cord has been unplugged.
It is still a further objective to allow the integration of monitoring and support equipment onto the frame of the bed to be powered by the bed to reduce the large number of medical personnel currently necessary to move a patient in the bed from room to room.
It is yet another objective to achieve all of the above objectives without increasing the leakage current on the bed frame and consequently increasing the chance of shock to a patient.